Method of making spring retaining caps



J. R.. COX

Feb. 16, 193.7.

2 Sheets-Sheet 2 Filed Aug. 26, 1935 f V////fl @WM Patented Feb. A16, "193,7-

UNITED STATES PArENr oFFlcE John R. Cox,

Cleveland, Ohio, assignor to Thompson Products, Incorporated, Cleveland, Ohio, a corporation of Ohio Application August 26, 1935, Serial No. 37,924

10 Claims.

This invention relates to a method of making spring retaining caps.

It has been the common practice heretofore in forming such caps to subject a suitable strip of metal to the action of a series of dies and punchers to form the caps and punch the same from the strip of metal as completed articles. This practice resulted in unduly thinning the walls of the caps at the tips. An alternate process existed in punching the metal directly through to form the individual caps, but this alternate process proved defective in that the metal broke out and produced a ragged edge on the tips of the cap.

This invention is designed to overcome the above noted defects in the provision of a practice that causes. a part of the metal in the web of the partially formed caps to flow into the wall thereof to thicken the same and at such an angle that a substantial right angle is formed between the end of the wall and the outer periphery thereof so that a square and unragged end is secured. The apparatus and practice is further designed to trap the metal at the flange of the cap to appreciably prevent the same from flowing from the wall and into the flange thereof.

The invention comprises the novel method hereinafter described and more particularly pointed out and dened in the appended claims.

In the accompanying drawings which illustrate a preferred form of apparatus involving this invention and designed to carry out the novel process, and in which similar reference numerals refer to similar features in the different views:

Figure 1 is a sectional View through an apparatus involving this invention.

Figure 2 is a plan view of a strip of metal illustrating the action of the different dies.

Figure 3 is an enlarged sectional View taken upon the line III-III of Figure l, looking in the direction of the arrows and showing parts in elevation.

Figure 4 is an enlarged sectional View taken upon the line IV-IV of Figure 1, showing parts in elevation and looking in the direction of the arrows.

Figure 5 is an enlarged sectional View through a completed cap,

In the process of forming the cap, a suitable strip of metal I is passed through the apparatus to receive successive actions from the dies and plungers. In the forward end of the apparatus or die press, there is a pair of dies 2 and 3 with which plungers 4 and 5 cooperate to extrude metal from said strip to form domes 6. Rearwardly of the die 3, there is a hollow die 'I shown more clearly in Figure 3. Through the die 'I there extends a plug 8 having an upper bevelled end 9. Adapted to cooperate with the die l, there is a punch Ill having a bevelled lower end II adapted to press against the web I2@ of the cap I2. The upper portion of the punch I 0 is enlarged and provided with a bevel I3 thatslopes upwardly from the outer circumference of said punch. The bevelled portion I3 of the punch is adapted to engage the strip of metal around the dome for initiating the ilange thereon.

As the punch Il) descends it will compress the web I2a or top of the dome and cause some of the metal therefrom to flow into the lower portion of the lateral wall of the cap. As this web is later punched out, it will be obvious that some of the waste metal is utilized for thickening the wall of the cap. It will be noted that the bevel 9 on the plug 8 is substantially at right angles to the periphery I4 of the cap, with the result that a substantially square and unragged end I2b is formed at the tip of the cap, as shown in Figure 5. It will further be evident that as the punch IEI descends, the bevelled face I3 will cause a downward bevel upon the metal designed to form the flange I2C of the cap, and that acts as a trap to prevent the metal from flowing outwardly in this and subsequent operations.

Rearwardly of the die 1, there is a hollow die I5 that retains the cap while a punch I6 descends for punching out the web of the cap, and a flange engaging die I5a flattens the iiange. The next operation is performed with the cap in a die I'I including the plug Ila, against which the tip of the cap is adapted to rest, as shown more clearly in Figure 4. The punch or pilot I8 cooperates with the die I'I for finishing the flange on the cap, as shown in Figure 4. 'Ihis pilot I8 has a tapered portion I8a for nally shaping the interior of the cap. The tapered portion I8a merges into a cylindrical portion |812 for smoothing the wall of the aperture in the cap, and in advance of the cylindrical portion I8b there is a novel tapered portion I 8c designed to pass through such aperture and gradually enlarge the same to the same size as the cylindrical portion I8b. The use of such a pilot 'I 8 possesses, several advantages. It eliminates an extra station and mechanism thereat for opening up the hole and prolongs the life of the pilot.

After a cap has been acted upon by the pilot I8, it is brought into operative relation with a shearing die I9 and a shearing punch 20 carrying a yieldingly mounted finishing plunger 2|.

While the operation of such a die press is well known, it might be mentioned that the metal strip is intermittently advanced after each operation. Before this can be done, it is of course necessary to elevate the die head. 'I'he strip will of course be advanced to bring the caps in the process of formation in operative relation with the different dies and plungers.

The operation of the apparatus results in the novel process of compressing' the bottom or web of the partially formed cap and causing the metal to flow into the lower portion of the wall thereof to thicken the same and simultaneously applying pressure at right angles to the end Wall of the cap adjacent such web to cause the metal to ow into such wall at substantially a right angle to the outer periphery of the cap whereby a full square edge is formed upon such end wall and a more even thickness of the wall is preserved.

At the same time, the bevel i3 is formed upon the flange of the cap to act as a trap for the material preventing the same from flowing outwardly whereby more material is gathered in the cap than would be possible with the usual square face on the flange.

The process further involves, as already noted, the punching of an aperture in the web of the cap and gradually enlarging the same to substantially the inner diameter of the cap.

It will be appreciated that the process produces an improved cap having a stronger cylindrical cup portion of more even thickness with a substantially square and clean cut end.

I am aware that many changes may be made in the method and apparatus for forming these caps without departing from the principles of this invention and I do not propose limiting the patent granted hereon otherwise than is necessitated by the prior art and the appended claims.

I claim as my invention:

1. The herein described method of making spring retaining caps which consists in punching a strip of metal for forming a dome, compressing the top portion of said dome for squeezing the metal into the adjacent Wall portion thereof, compressing the strip of metal surrounding said dome portion to produce an outwardly and downwardly directed slope, punching an aperture in said compressed top, compressing said surrounding portion to form a flange and shearing said cap from said strip.

2. The herein described method of making spring retaining caps which consists in forming a dome in a strip of metal, squeezing the top of the dome to cause metal to flow intothe adjacent lateral wall to thicken the same, forming an aperture in the top of the dome, forming a flange around the dome, and shearing the cap from said strip.

3. The herein described method of making spring retaining caps which consists in forming a dome in a strip of metal, acting upon the to-p portion of said dome to cause metal to ilow into the lateral wall at substantially a right angle, perforating the top of said dome, forming a flange around said dome, and shearing the cap from said strip of metal.

4. The herein described method of making spring retaining caps which consists in punching a dome in a strip of metal, compressing the top of said dome and adjacent parts of said metal to cause metal to flow into the lateral Wall of said dome, perforating the top of said dome, forming a flange therearound, and shearing the cap from said strip.

5. The herein described method of making spring retaining caps which consists in punching a cup shaped portion in a strip of metal, squeezing the closed end of said cup shaped portion for causing metal to flow into the lateral wall thereof, conning the flow of said metal to a substantial right angle to form a square edged lateral wall, perforating the closed end of said cup shaped portion and forming a flange around the other end thereof, and shearing such flanged cup from said strip of metal.

6. The herein described method of making spring retaining caps which consists in punching a dome in a strip of metal, squeezing the top of said dome to cause metal to flow into the lateral wall, forming an aperture in the top of said dome, gradually enlarging said aperture, forming a flange around said dome, and shearing the completed cap from said strip of metal.

7. The herein described method of making retaining caps which consists in forming a domein a strip of metal, squeezing said dome in parallel planes and applying pressure at substantially a right angle to the end of the wall portion thereof for causing the metal to flow into such wall portion and causing a square end on said wall portion, forming a flange around said dome, punching an aperture in said compressed top of said dome and shearing the formed cap from said strip of metal.

8. The herein described method of making retaining caps which consists in forming a dome in a strip of metal, squeezing the top of said dome to a thin web and causing the metal thereof to flow into the adjacent wall thereof, forming a trap in the metal surrounding said dome, forming the metal surrounding said dome into a flange, forming an aperture in said web and shearing the formedcap from said strip.

9. The herein described method of making spring retaining caps which consists in forming a dome in a metal strip, compressing the top of said dome to a relatively thin web and causing the metal to iiow into the adjacent wall portion to thicken the same, forming a downwardly and outwardly extending slope in the metal surrounding said dome to act as a trap, forming a liange around said dome, perforating said web and shearing the formed cap from said strip.

10. The herein described method of making retaining caps which consists in forming a dome in a strip of metal, applying pressure to both sides of said dome to reduce the same to a web, and causing the metal to flow into the adjacent lateral Wall of said dome and simultaneously applying pressure at a right angle to one end of the wall, forming a flange around said wall, perforating said web and shearing said cap from said strip.

JOI-IN R. COX. 

